1. Field of the Invention
The present invention relates to devices for paper feeding and alignment, and more particularly to devices for paper feeding and alignment in a printer such as an ink-jet printer.
2. Discussion of Related Art
Devices such as printers have paper feeding devices for feeding papers stored in a paper tray to the printing mechanism. A pickup roller is mounted in a typical feeding device, and papers are fed sheet by sheet by friction between paper loaded on a paper feeding plate (or knock up plate) and a powered pickup roller. There are two kinds of pickup roller methods in general use: one is a method using a circular pickup roller, and the other is a method using a semicircular pickup roller.
The method of arranging papers in a device using a circular pickup roller is described as follows. A paper is transported from a paper load cassette by rotation of a pickup roller. A paper transported by the pickup roller is transported to the contact line of a feed roller and a pinch roller, rotating in the counter direction to the paper processing direction. The front edge of the paper and the contact line of the feed roller and a pinch roller coincide exactly because a curl occurs in the fed paper. The feed roller then rotates in the forward direction (paper processing direction), and the pickup roller enters an idling state in which driving power is intercepted. However, this method produces a load on the paper on the paper feed plate from the pickup roller.
The most important reason that a semicircular pickup roller is adapted is to eliminate the load on a paper after the paper feeding is finished. That is, as feeding is finished, the transported paper becomes free as the paper feeding plate exchanges with the pickup roller. In this method, no curl occurs on a paper due to a counter rotation, and it is essential that a guide in the horizontal direction and at right angle to a feed roller be used for preserving the proper orientation of the paper. Therefore, a side of a paper is guided using a guide without a diversion. When papers are fed separated, sheet by sheet, however, any resistance to one side of a paper by, for example, the user's finger, will lead to distortion at the time of feeding in spite of using a guide. Also, in some devices two pickup rollers are used. Here, the feeding direction can be misguided and distorted due to inequality of input/output of the pickup rollers.
Based on my observation of the art, then, I have discovered that what is needed is a paper aligning apparatus which avoids the problem of continuous load on the paper seen with circular pickup rollers, and the problem of misguiding seen with semicircular pickup rollers.